The past few years have seen remarkable progress in the HIV prevention field. Topical microbicides have had their first, modest demonstration of efficacy in women using tenofovir gel. Throughout the last six years the Microbicide Trials Network (MTN) has laid a foundation of additional studies to gird the clinical microbicide infrastructure. Over the next seven years, the MTN plans to expand the drugs and dosage forms brought into HIV prevention and we will focus our efforts on populations that are at high risk for HIV acquisition. As the Laboratory Center (LC) for the MTN we will provide laboratory oversight for the MTN scientific agenda to ensure compliance of all laboratories to good clinical laboratory practice. Additionally, the MTN LC will work with all NIH-sponsored HIV clinical trial networks and NIH contractors to harmonize laboratory methods and maximize the efficiency of protocol implementation. This will develop clear lines of communication between the MTN LC and associated Clinical Trials Units/Clinical Research Sites laboratories. Secondly, the MTN LC will work with the MTN Leadership Group and Statistical and Data Management Center to ensure the MTN scientific agenda continues to be responsive to protocol requirements for product safety and anticipated product efficacy. To accomplish our mission, the MTN LC will rely on three Core Laboratories: the Protocol Support Core led by Dr. Charlene Dezzutti along with Drs. Lisa Rohan, Sharon Hillier and lan McGowan who will provide their expertise for product testing, site support, sexually transmitted disease diagnoses, mucosal flora monitoring, mucosal immunity, and systems biology; the Virology Core led by Dr. John Mellors and Dr. Urvi Parikh who will provide the daily oversight for the HIV endpoint and drug resistance testing - primary endpoints for our protocols; and the Pharmacology Core led by Drs. Craig Hendrix and Peter Anderson who will provide their expertise for analyte analysis and assay development and define how much drug reaches the target tissue/cells and how long it remains - critical questions for topical microbicide development. Together, this remarkable team will strive to bring to licensure a safe and effective topical microbicide.